CN108386278B

CN108386278B - Dual fuel cylinder deactivation control system and method

Info

Publication number: CN108386278B
Application number: CN201810094253.8A
Authority: CN
Inventors: N·阿特贝里; M·J·恩格费; 许华
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2017-02-03
Filing date: 2018-01-31
Publication date: 2022-04-26
Anticipated expiration: 2038-01-31
Also published as: US20180223745A1; US11105278B2; CN108386278A; DE102018102192A1

Abstract

An engine control system includes a dual-fuel internal combustion engine, a fuel system including a liquid fuel source and a gaseous fuel source, and a controller. The engine control system further includes a liquid fuel control module and at least one gaseous fuel control module associated with the first and second cylinder subgroups, each communicatively connected via a network. The controller has an operating mode and a cylinder deactivation mode. In the operating mode, the controller is configured to instruct the liquid fuel control module and the at least one gaseous fuel control module to operate the plurality of cylinders in the dual fuel mode. A controller in the cylinder deactivation mode transitions the plurality of cylinders to a liquid fuel only mode during the gradual stop, deactivates the first cylinder subset, and then transitions to a dual fuel mode in the second cylinder subset.

Description

Dual fuel cylinder deactivation control system and method

Technical Field

The present disclosure relates generally to engine control systems and methods, and more particularly to an engine control system for a dual-fuel engine having dual-fuel control and cylinder deactivation strategies.

Background

Cylinder deactivation is a method of reducing or completely stopping combustion in one or more cylinders of an engine. Cylinder deactivation is typically activated during light engine load to improve efficiency and reduce fuel usage. Deactivation is particularly useful for work machines having long periods of inactivity where the engine remains running under light loads. Typically, one or more cylinders are deactivated while the active cylinder subset continues to be operated. For single fuel engines (e.g., diesel engines, etc.), a simple fuel strategy to stop injection is sufficient. However, for dual fuel engines in which gaseous and liquid fuels are combusted, improved fueling strategies are needed. In some dual fuel engines, gaseous fuel may be injected at up to 500 crank degrees before top dead center, causing a substantial phase delay between injection and combustion. Such phase delays may interfere with existing cylinder deactivation control techniques and may result in misfire during cylinder deactivation or dual ignition when the cylinder is activated. Furthermore, for a dual fuel engine with separate control modules for each fuel type, the ability to control the precise amount of fuel in each cylinder at any given time is further limited due to the nature of the electronic and communication protocols between the control modules, which can exacerbate the phase delay problem. Therefore, there is a need for a robust cylinder deactivation method that ultimately allows for increased gas substitution within the cylinder when separate control modules are used to control the injection of each fuel.

An engine control method and system for deactivating cylinders in a bi-fuel engine is described in PCT publication No. WO2016/154086a1 ('086 publication) (published by Kolhouse et al, 9/29/2016). The' 086 publication describes an engine control system that reduces gaseous fuel injection in a targeted cylinder bank designated as deactivated while continuing to maintain dual fuel combustion in the remaining cylinders.

While the method and system of the' 086 publication may address the issues of dual-fuel engines with respect to its effect on exhaust and injector requirements, it does not address the issues related to phase delays in gas injection and cylinder deactivation and activation requests. It also fails to address the problem of double ignition or misfire when deactivating or activating cylinders of a dual fuel engine.

The disclosed system is directed to overcoming one or more of the problems set forth above.

Disclosure of Invention

In one aspect, the present disclosure is directed to an engine control method that includes operating a dual-fuel internal combustion engine including a plurality of cylinders configured to receive a liquid fuel and a gaseous fuel. The method includes determining a cylinder deactivation event and entering a cylinder deactivation mode after determining the cylinder deactivation event, including identifying a first cylinder subset to be deactivated, decreasing an amount of gaseous fuel relative to liquid fuel from an initial amount during a gradual stop of a plurality of cylinders, deactivating the first cylinder subset while continuing to operate the activated cylinder subset, and increasing the amount of gaseous fuel relative to liquid fuel during the gradual start of the activated cylinder subset.

In another aspect, the disclosure is directed to an engine control method that includes operating a dual-fuel internal combustion engine including a plurality of cylinders configured to receive a liquid fuel and a gaseous fuel, a liquid fuel control module, a first gaseous fuel control module associated with a first cylinder subgroup, and a second gaseous fuel control module associated with a second cylinder subgroup. The method includes determining a cylinder deactivation event and entering a cylinder deactivation mode after determining the cylinder deactivation event. Entering the cylinder deactivation mode includes instructing the first and second gaseous-fuel control modules to reduce an amount of gaseous fuel in the plurality of cylinders relative to liquid fuel from an initial amount during the gradual stop while instructing the liquid-fuel control module to continue operating the plurality of cylinders with liquid fuel during the gradual stop; deactivating the first cylinder subset by instructing the liquid fuel control module to stop injecting liquid fuel in the first cylinder subset while continuing to inject liquid fuel in the second cylinder subset; and instruct the second gaseous-fuel control module to increase the amount of gaseous fuel relative to the liquid fuel to the initial amount during the gradual start of the second cylinder subset.

In yet another aspect, the present disclosure is directed to an engine control system that includes a dual-fuel internal combustion engine having a plurality of cylinders configured to receive a liquid fuel and a gaseous fuel, a fuel system including a liquid fuel source and a gaseous fuel source, and a controller. The engine control system further includes a controller, a liquid fuel control module, and at least one gaseous fuel control module associated with the first cylinder subgroup and the second cylinder subgroup, each communicatively connected via a network. The controller has an operating mode and a cylinder deactivation mode. The controller in the operating mode is configured to instruct the liquid fuel control module and the at least one gaseous fuel control module to operate the plurality of cylinders in a dual fuel mode. The controller in the cylinder deactivation mode is configured to instruct the liquid fuel control module and the at least one gaseous fuel controller to transition to the liquid fuel only mode during the gradual stop; instructing the liquid fuel control module to deactivate the first cylinder subset by ceasing injection of liquid fuel into the first cylinder subset while continuing to inject liquid fuel into the second cylinder subset during the gradual stop; and after deactivating the first cylinder subgroup, instructing the liquid fuel control module and the at least one gaseous fuel control module to transition to the dual fuel mode in the second cylinder subgroup.

Drawings

FIG. 1 is a schematic illustration of an exemplary disclosed engine control system;

FIG. 2 is a flow chart illustrating an exemplary disclosed method of operating the engine control system of FIG. 1;

FIG. 3 is another flowchart illustrating an exemplary disclosed method of operating the engine control system of FIG. 1; and is

FIG. 4 is a graph illustrating exemplary fuel delivery of gaseous and liquid fuels for the disclosed method.

Detailed Description

FIG. 1 provides a schematic illustration of an exemplary disclosed engine control system. The system includes a dual fuel engine 20 having an engine block 21 defining a plurality of engine cylinders 22. A piston reciprocates in each cylinder 22 to determine a compression ratio that is typically associated with a compression ratio suitable for compressing a liquid for ignition injection, such as diesel fuel. In the illustrated embodiment, the engine 20 includes twelve engine cylinders 22. However, those skilled in the art will appreciate that engines having any number of cylinders will also fall within the intended scope of the present invention.

The engine 20 includes a fuel system that supplies liquid and gaseous fuels to the cylinders 22 for combustion. Liquid fuel injectors 30 are positioned to inject liquid fuel directly into each of the plurality of cylinders 22. The fuel system may include a high-pressure gaseous fuel common rail and a liquid fuel common rail, or the fuel system may include a low-pressure fuel pump having unit injectors. In either embodiment, the fuel system includes a liquid fuel source 29 that supplies liquid fuel (e.g., diesel fuel) to the engine 20 and a gaseous fuel source 28 that supplies gaseous fuel (e.g., compressed natural gas) to the engine 20.

Gaseous fuel source 28 may include a pressurized cryogenic liquid natural gas tank 31 having an outlet fluidly connected to a variable delivery cryogenic pump 36. Although not all shown in fig. 1, gaseous fuel source 28 may also include a heat exchanger, an accumulator, a fuel conditioning module that controls the pressure of the gaseous fuel supplied to engine 20, and a gas filter 34. Liquid fuel source 29 may include a diesel fuel tank 37, a fuel filter 38, and a fuel pump 39 that supplies liquid fuel to engine 20 and controls the pressure delivered to engine 20. Additional controls, including shut-off valves, may be located between the pressurized cryogenic liquid natural gas tank 31 and the engine 20 to isolate the tank 31 from the engine 20.

The gas and

liquid fuel lines

40, 41 may supply fuel to the engine 20. For purposes of the present disclosure, engine 20 is illustrated and described as having twelve cylinders arranged in a first bank 23 and a second bank 24. However, those skilled in the art will recognize that the engine 20 may include a greater or lesser number of cylinders, and that the cylinders 22 may be disposed in an "in-line" configuration, a "V" configuration, an opposed configuration, or any other suitable configuration. Fuel from

lines

40, 41 is delivered to the engine 20 through individual fuel injectors 30 and intake valves 32. Fuel injector 30 injects liquid fuel directly into cylinder 22, while intake valve 32 releases gaseous fuel upstream of cylinder 22. This may include injecting gaseous fuel in the intake manifold or upstream of a turbocharger ambient air intake (not shown). By way of example, fuel injector 30 may be implemented as an electronically actuated injector (e.g., an electronically controlled unit injector, mechanically actuated), an electronically controlled injector, a digitally controlled fuel valve, or any other type of fuel injector known in the art. Each fuel injector 30 and intake valve 32 may be separately and independently operable to inject an amount of pressurized fuel into the associated cylinder 22 at predetermined timings, fuel pressures, and fuel flow rates.

A piston (not shown) may be slidably disposed within each cylinder 22 to reciprocate between a top-dead-center position and a bottom-dead-center position while the crankshaft is fully rotated. During rotation, the piston undergoes an intake stroke, a compression stroke, a combustion or power stroke, and an exhaust stroke. The pistons may be operatively connected to the crankshaft via a plurality of connecting rods. The crankshafts may be rotatably disposed within the engine block 21 and operatively connected to a generator or to a mechanical transmission such that rotational movement of each crankshaft causes a corresponding rotation of the connected generator or transmission.

During a diesel cycle, the pistons may move from a top-dead-center position to a bottom-dead-center position through an intake stroke to draw air into the respective cylinders 22. The piston may then return to the top dead center position, thereby compressing air during the compression stroke. Near the end of the compression stroke and/or during the first portion of the power stroke, the fuel injector 30 and intake valve 32 associated with each cylinder 22 may deliver pressurized injections of liquid fuel and gaseous fuel, respectively, to the cylinder 22. The pressurized injection may mix with pressurized air within the cylinder during the compression stroke and cause combustion of both liquid and gaseous fuels. When ignited, the air-fuel mixture may cause the piston to move back to a bottom dead center position during the power stroke. This downward movement of the piston powers the rotational movement of the crankshaft and thus the rotational movement of the generator or transmission. The piston may then return to the top dead center position to expel exhaust gases from the cylinder 22 during the exhaust stroke.

In the present embodiment, engine 20 is a dual fuel engine configured to combust two different types of fuel and produce a mechanical output that drives a machine or generator. The engine 20 may operate in a liquid fuel only mode, wherein liquid fuel is only injected into the cylinders 22, or a dual fuel mode, wherein liquid and gaseous fuels are injected and enter the cylinders 22. Which fuel to inject, how much of each type of fuel to inject, and when to inject each fuel are determined by a controller 81 in communication with the at least one liquid fuel control module 71 and the at least one gaseous fuel control module 61, 62. Although fig. 1 illustrates the first gas fuel controller 61 and the second gas fuel controller 62, the system may include embodiments having only one gas fuel controller.

The controller 81, the at least one liquid fuel control module 71, and the at least one gaseous fuel control module 61, 62 are each communicatively connected via a network (e.g., a CAN network). In one embodiment, the first gaseous fuel control module 61 may be associated with a first cylinder subgroup, while the second gaseous fuel control module 62 may be associated with a second cylinder subgroup. Each subgroup may include a cylinder bank, with the first cylinder subgroup including a first cylinder bank 23 and the second cylinder subgroup including a second cylinder bank 24.

In some situations, it may be desirable to have some of the cylinders 22 of the engine 20 operable. The controller 81 has an operating mode and a cylinder deactivation mode. The cylinder deactivation mode may be triggered when a controller 81, which monitors various parameters of the engine and associated machinery, determines a cylinder deactivation event. When a cylinder deactivation event is determined, the controller 81 may enter a cylinder deactivation mode and instruct the at least one liquid fuel control module 71 and the at least one gaseous fuel control module 61, 62 to initiate the step of deactivating one or more cylinders 22 of the engine 20. This allows the engine 20 to continue operating with less than all of the cylinders 22 active, thereby injecting less fuel and reducing consumption.

The cylinder deactivation event may correspond to, for example, low engine speed, low engine load, a period of inactivity, and/or cold operation. Specifically, at low engine speeds and/or low loads, the amount of fuel injected by any one of fuel injector 30 and intake valve 32 may be relatively small. It should be understood that total injected fuel may refer to total liquid fuel in the liquid fuel only mode, or total liquid and gaseous fuel in the dual fuel mode. Generally, when the total injected fuel falls below a threshold, the efficiency of engine 20 may be affected (e.g., reduced) or the gas displacement capability of engine 20 may be limited due to mechanical or generator parasitic losses. During such conditions, only a portion of the cylinders 22 may be operating such that the total amount of injected fuel is reduced and/or distributed among fewer injectors 30 is better. In some cases, fuel injector 30 may inject a greater and more efficient amount of fuel when only a portion of the cylinders are active. Alternatively, fewer injectors may be operated with the same amount of fuel injected prior to deactivating any cylinders. During cold operation, the amount of fuel injected by any one of fuel injectors 30 may be too small to adequately warm engine 20. In such a case, it may again be advantageous to use fewer activated cylinders 22, such that each activated fuel injector 30 and intake valve 32 may inject a greater amount of fuel, and thereby allow more gas displacement to occur in the activated cylinders 22 relative to operating all of the cylinders 22. Thus, in some cases, a subset of the cylinders 22 may be deactivated (i.e., a subset of the fuel injectors 30 and intake valves 32 may stop injecting fuel into the engine 20). The control process for deactivating and activating each cylinder (or cylinder subset) is described in further detail below.

To regulate operation of fuel injectors 30 and intake valves 32 and selectively deactivate cylinders 22, controller 81 communicates with at least one liquid fuel controller 71 and at least one gaseous fuel controller 61/62 and indicates how and when to inject fuel into engine 20. Controller 81 may receive input from one or more sensors on the machine and in engine 20, and may also receive input from an operator. Input from sensors may indicate a cylinder deactivation event to controller 81, or alternatively, input from an operator may be used to manually trigger a cylinder deactivation mode. Controller 81 is configured to output signals to at least one liquid fuel controller 71 and at least one gaseous fuel controller 61/62 providing deactivation commands to the modules. Accordingly, the controller 81 may determine a need to deactivate one or more cylinders 22 and responsively adjust the operation of the fuel injectors 30 and the intake valves 32 via the modules 71, 61, 62 to accommodate particular operating conditions of the engine 20 and/or input from an operator.

Controller 81, at least one liquid fuel controller 71, and at least one gaseous fuel controller 61/62 may each be embodied as a single or multiple microprocessors, Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), etc., including devices for controlling the operation of engine 20 in response to various inputs. Many commercially available microprocessors are configured to perform the functions of each of controller 81, at least one liquid fuel controller 71, and at least one gaseous fuel controller 61/62. Various other known circuits may be associated with controller 81, at least one liquid fuel controller 71, and at least one gaseous fuel controller 61/62, including power supply circuitry, signal conditioning circuitry, actuator driver circuitry (e.g., circuitry to power solenoids, motors, or piezoelectric actuators), communication circuitry, and other suitable circuitry.

The controller 81 is configured to determine the number of cylinders 22 to deactivate (i.e., the number of fuel injectors 30 and intake valves 32 to prevent fuel from being supplied to the associated cylinders 22) such that the performance of the engine 20 is substantially maintained at or returned to a desired operating range. In one example, the controller 81 may reference one or more relational maps stored in memory based on signals from one or more sensors and/or based on another input. Each of these maps may include a collection of data in the form of tables, graphs, and/or equations. One such relationship map may, for example, relate a desired output of the engine (i.e., torque and/or speed) to an amount of fuel that must be injected into and combusted within the engine. The same or a different relationship map may then relate the amount of fuel to a plurality of fuel injectors 30 and intake valves 32 that should be operable to inject the amount of fuel and still maintain the desired efficiency and/or desired temperature 20 of the engine, and the corresponding remaining number of cylinders 22 (i.e., a subset of cylinders 22) should be deactivated. In some embodiments, when the cylinders 22 are deactivated, the amount of fuel injected into any one of the cylinders 22 to maintain operation may be increased to maintain the same mechanical output. The controller 81 is configured to determine and implement the increased fueling and simultaneously disable the cylinders 22 by a proportional amount.

When adjusting the operation of fuel injector 30, controller 81 may directly control liquid fuel control module 71 to generate and send a fuel delivery change signal to fuel injector 30. These signals may be used to adjust fuel delivery rate, fuel delivery timing, fuel delivery pressure, and/or fuel torque limits. These fuel delivery change signals may be generated based on engine control maps such as a rail pressure map, a timing map, a torque limit map, etc., as is known in the art. The fuel delivery change signal may be delivered to all of the fuel injectors 30 associated with a particular liquid fuel module 71 or to a subset of the fuel injectors 30 associated with a particular liquid fuel module 71.

In one embodiment, a particular subset of cylinders 22 may vary between deactivation events, or a designated subset of cylinders 22 (e.g., first bank 23 or second bank 24) may be deactivated at once. Further, deactivated and activated cylinders 22 may be swapped after undergoing a deactivation cycle, after which the deactivated cylinders are activated and vice versa. For example, in a twelve cylinder engine, it may be fairly common to selectively disable four or even six of the twelve cylinders 22. Between deactivation events, the controller 81 may select a different cylinder 22 to be included in the next subset of cylinders 22 to be deactivated. In this manner, none of the cylinders 22 may be operated or not operated significantly more than any other cylinder 22. However, in one embodiment, the first bank 23 may be deactivated when the second bank 24 is activated, and the two may exchange states after each deactivation cycle. The deactivation cycle may be a predetermined period of time set by the controller 81 such that the cylinders 22 alternate between deactivation and activation in a uniform pattern. Alternatively, the deactivation cycle may incorporate inputs from various sensors that modify the length of the deactivation cycle based on which cylinder is deactivated/activated and the state of the engine (e.g., whether a side of the engine is too cold, whether a fault is being recorded, etc.). Thus, in this embodiment, the deactivation cycle may be variable and change based on input from sensors and other inputs.

In one embodiment, during the transition from the first to the second subset of deactivated cylinders 22, all cylinders 22 of the second subset may be deactivated as a whole at about the same time that the first subset of cylinders 22 is reactivated (e.g., activated). For example, in a twelve cylinder engine in which six cylinders 22 have been deactivated, another subset of six cylinders 22 may be deactivated all at once, and the first subset of six cylinders 22 reactivated substantially simultaneously. In most cases, the number of cylinders 22 in each subgroup may be approximately equal. However, in other embodiments, the number of cylinders 22 deactivated at any one time may be variable. Further, a time delay may be used between cylinder deactivation such that there is overlap between deactivated cylinders and activated cylinders.

Industrial applicability

The disclosed engine control system may be applicable to any machine that includes an internal combustion engine powered by liquid and gaseous fuels. The disclosed engine control system may improve cylinder deactivation of such dual-fuel internal combustion engines by allowing gaseous fuel to be exhausted from the engine cylinders before deactivating the liquid fuel injectors. This solves the problem associated with phase delay between the release of gaseous fuel into the cylinder and combustion in the cylinder that is desired to be deactivated. This also solves the problems associated with controlling the liquid and gaseous fuel content in the cylinders 22 when separate control modules for liquid and gaseous fuels are used. The operation of the engine control system will now be explained.

For a dual fuel engine 20, an intake valve 32 allows gaseous fuel to enter the cylinder 22, and an injector 30 injects liquid fuel directly into the cylinder 22. Operation of the intake valve 32 is controlled by one or more gaseous fuel control modules 61, 62, while operation of the injector 30 is controlled by one or more liquid fuel control modules 71. Because two different fuel delivery techniques are used, the operation of intake valve 32 is not synchronized with fuel injector 30. Furthermore, there is a significant phase delay between the operation of the intake valve 32 and the combustion of the gaseous fuel in the cylinder 22. Therefore, the controller 81 cannot stop the injection of the gaseous fuel and the liquid fuel at the same time at any one time. Furthermore, communication signals on the communication network cannot be synchronized. Therefore, it is preferred to first disable the release of gaseous fuel into the cylinder while continuing to inject liquid fuel to allow gaseous fuel to combust in the cylinder 22 before deactivation is triggered.

Referring to FIG. 2, operation of the engine control system is shown. The control method includes operating a dual fuel internal combustion engine (step 200) having a plurality of cylinders configured to receive a liquid fuel and a gaseous fuel. During engine operation, the controller 81 receives inputs from various sensors within the engine, the machinery supporting the engine, and the operator (step 201). The sensor inputs may include, among other things, engine load, engine speed, engine torque, coolant temperature, oil temperature, intake manifold temperature, ambient air temperature, and intake air temperature. The operator input may include an input manually triggered by a machine operator or a system operator that signals the controller 81 to take a particular action, such as entering or leaving a cylinder deactivation mode. The controller 81 receives these inputs and monitors their values to determine if the sensor signal is within a predetermined range. The predetermined range may include a desired or acceptable range before the engine may enter the cylinder deactivation mode. Finally, the controller 81 monitors for any diagnostic faults associated with the engine, including any registered component faults, failed processes, or failed checks normally handled by the controller 81 and/or a separate controller.

Next, the controller 81 may determine a cylinder deactivation event from the inputs (step 202). In one embodiment, the controller 81 determines a cylinder deactivation event when the engine load is below a threshold load and the engine speed is below a threshold speed for a predetermined period of time. In other embodiments, the controller 81 additionally determines a cylinder deactivation event by also determining whether one or more of the coolant temperature, intake manifold temperature, ambient temperature, and intake air temperature are within predetermined ranges and by determining that a diagnostic fault has not been triggered. In yet another embodiment, the controller 81 determines the cylinder deactivation event by receiving a cylinder deactivation mode input from an operator. If a cylinder deactivation event is not determined (NO in step 202), the process returns to step 201 and continues to receive input until the controller 81 can determine a cylinder deactivation event. Upon determining a cylinder deactivation event (step 202, yes), controller 81 may enter a cylinder deactivation mode (step 203).

FIG. 3 provides a flow chart of controller 81 in cylinder deactivation mode. Upon determining a cylinder deactivation event (step 202, yes) and entering a cylinder deactivation mode (step 203), in one embodiment, controller 81 may identify a subset of cylinders to deactivate (step 204). The subset may include one or more cylinders or one or more banks of cylinders. The cylinder subsets may also include all of the activated cylinders or a subset of the activated cylinders, where another cylinder subset has been deactivated (e.g., a subset of the alternately deactivated cylinders).

Prior to deactivating the cylinder subset identified in step 204, the controller 81 may enter liquid fuel only mode for all activated cylinders (step 205). The liquid fuel only mode includes the controller 81 instructing the one or more liquid fuel control modules 71 and the one or more gaseous fuel control modules 61, 62 to gradually stop admitting gaseous fuel to the activated cylinders while continuing to inject liquid fuel. The flow rate and duration of liquid fuel injected by the liquid fuel injectors 30 may be increased or otherwise varied by the liquid fuel control module 71 to compensate for the depletion of gaseous fuel in the cylinders 22 to maintain a constant power output of the engine or a constant controlled engine speed. During this process, the controller 81 instructs one or more of the gaseous fuel control modules 61, 62 to reduce the gaseous fuel from an initial amount relative to the amount of liquid fuel during the gradual stop of the plurality of cylinders. In some embodiments, the amount of gaseous fuel relative to liquid fuel is reduced to zero (e.g., only liquid fuel is introduced into the activated cylinders).

Once the activated cylinders of engine 20 are operating in liquid fuel only mode (e.g., liquid fuel only operation), controller 81 instructs at least one liquid fuel control module 71 to deactivate the identified subset of cylinders from step 204 to be deactivated (step 207). After simultaneous or just subsequent deactivation in step 207, the controller 81 instructs the at least one liquid fuel control module 71 to continue operating the activated cylinder subset (step 206). In this step, the activated cylinder subset is fueled by liquid fuel injectors 30 and operated in the liquid fuel only mode. After the identified cylinder subset has been deactivated and the activated cylinder subset is maintained, the controller 81 may instruct the at least one gaseous fuel control module 61, 62 and the at least one liquid fuel control module 71 to cause the activated cylinder subset to enter a dual fuel mode (step 208). In this step, the at least one gaseous fuel control module 61, 62 and the at least one liquid fuel control module 71 increase the amount of gaseous fuel relative to liquid fuel during the gradual start of the activated cylinder subset. Once the gradual start period is over, the appropriate ratio of gaseous fuel to liquid fuel is introduced to the active cylinders to meet the demand according to the above-described relationship map. In some embodiments, this requires increasing the amount of gaseous fuel to the initial amount (e.g., prior to the liquid fuel only mode).

Once the dual fuel mode has been achieved for the activated cylinder subset in step 208, the controller 81 continues to operate the activated cylinder subset for the deactivation cycle. A deactivation cycle is a period of time during which the engine operates a cylinder subset and deactivates another cylinder subset. As described above, the duration of the time period may be affected by various inputs, or it may be uniform. Accordingly, the controller may determine whether the deactivation cycle has been completed (step 209), after which the process returns to step 204 and the controller 81 identifies another cylinder subset to be activated. The process may repeat, with different cylinder subsets deactivated and activated in each cycle, or alternating between two or more banks that are activated and deactivated. If the deactivation cycle is not complete in step 209, the controller 81 may continue to monitor inputs (step 210) and maintain the activated cylinder subset until sensor data, operator input, or other input triggers the controller 81 to exit the cylinder deactivation mode (step 211).

If the deactivation cycle is complete in step 209, the controller 81 may identify a second cylinder subset to be deactivated, enter liquid fuel only mode for the activated cylinders, deactivate the second cylinder subset while maintaining the second activated cylinder subset, and then enter dual fuel mode for the second activated cylinder subset. The process may continue until cylinder deactivation mode is exited (step 211). Further, at any time during this process, the controller 81 may exit the cylinder deactivation mode and activate all of the cylinders 22 of the engine 20. This may need to be based on sensor input or operator input.

To exit the cylinder deactivation mode, the deactivated cylinders must be activated. To do so, the controller 81 causes the activated cylinder subset to enter the liquid fuel only mode. In the liquid fuel only mode, the active cylinders currently operating in the dual fuel mode are instructed to operate using liquid fuel only. The controller 81 instructs at least one of the gaseous fuel control modules 61, 62 to stop injecting gaseous fuel while instructing the liquid fuel control module 71 to inject liquid fuel into the activated cylinder subset during the gradual stop. Once the engine is operating in the liquid fuel only mode (e.g., using only liquid fuel injectors), the controller activates all of the cylinders 22 of the engine 20 after the gradual stop period by instructing the liquid fuel control module 71 to inject liquid fuel into the deactivated subset of cylinders. Once all cylinders are activated using liquid fuel, the controller 81 enters a dual fuel mode for all cylinders by instructing at least one gaseous fuel control module 61, 62 to increase the amount of gaseous fuel relative to liquid fuel during the step start. According to the above-described relationship map, the liquid fuel control module 71 may compensate for the introduction of gaseous fuel by injecting more or less liquid fuel.

Thus, each instance of cylinder deactivation is accompanied by a first transition to a liquid fuel only mode, wherein no gaseous fuel is introduced into the cylinder and the liquid fuel injector continues to inject liquid fuel in the activated cylinder. Once gaseous fuel is combusted in the cylinder during the gradual stop, the identified cylinder may be deactivated. Once deactivated, gaseous fuel may be reintroduced into the activated cylinders. This process is repeated when the activation/deactivation of cylinders is alternated or changed or the cylinder deactivation pattern is left.

As shown in the graph of FIG. 4, an embodiment of an engine control system is presented that shows gaseous fuel content and liquid fuel content in a cylinder over time. The liquid fuel injector 30 introduces liquid fuel directly into the cylinder 22 via direct injection. Liquid fuel injector 30 may therefore be stopped and started with minimal time delay or phase difference between injection and engine crank angle position. Intake valve 32 introduces gaseous fuel upstream of the cylinder, creating a delay between intake and combustion. Thus, to prevent gaseous fuel from being trapped in deactivated cylinders, in one embodiment, gaseous fuel is stopped during a gradual stop while the liquid fuel injector continues to operate while entering the liquid fuel only mode. This allows gaseous fuel to be combusted in the cylinder, and the cylinder continues to operate with liquid fuel. Once all of the gaseous fuel is combusted during the gradual stop, the liquid fuel injectors may be deactivated and the cylinders deactivated.

As shown in FIG. 4, the transition from a previously deactivated cylinder to an activated cylinder is shown at time t 1. Liquid fuel injector 30 is activated in the previously deactivated cylinder, as indicated by line 152 at time t 1. The intake valve allows gaseous fuel to enter the cylinder during the gradual start, represented by line 156 between times t1 and t 2. Once the gradual start period has elapsed at time t2, the cylinder is operating in the dual fuel mode, represented by line 158 between times t2 and t 3. As more gaseous fuel is introduced, the amount of injected liquid fuel may be varied, as indicated by dashed line 155. After the deactivation cycle is complete, or based on an alternative input, the controller 81 may identify the deactivated cylinders at time t 3. To deactivate the cylinder, the cylinder is switched to liquid fuel only mode and the amount of gaseous fuel is reduced relative to liquid fuel during the gradual stop, represented by line 157 between times t3 and t 4. Once the cylinder is operating in the liquid fuel only mode and gaseous fuel has been combusted within the cylinder during the step-down, the cylinder may be deactivated at time t 4. Liquid fuel injector 30 stops injecting liquid fuel into the cylinder at line 153. FIG. 4 is a chart illustrating one embodiment of an engine control method. The relationship between the amount of each fuel and the amplitude shown in the graph is not proportional. The amounts of gaseous fuel and liquid fuel introduced into the cylinder are controlled by the above-described relational map, and are controlled by the controller 81 and the respective modules.

The present engine control system may have several advantages over the prior art. These advantages include providing a more robust deactivation strategy when using gaseous and liquid fuels to fuel the engine. The present engine control system provides a method of deactivating a dual fuel cylinder, particularly under light load conditions, which eliminates potential double ignition conditions from the residual gaseous fuel. Further, the present engine control system may allow the dual fuel engine to operate and deactivate cylinders while operating with a lower amount of gaseous fuel than typical methods.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed engine control system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed engine control system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. An engine control method comprising:

operating a dual fuel internal combustion engine comprising a plurality of cylinders configured to receive a liquid fuel and a gaseous fuel;

determining a cylinder deactivation event; and is

Entering a cylinder deactivation mode after determining the cylinder deactivation event, comprising:

identifying a first subset of cylinders from the plurality of cylinders to be deactivated;

gradually reducing the amount of gaseous fuel relative to the liquid fuel from an initial amount during a gradual stop for all of the plurality of cylinders, and then stopping injecting gaseous fuel;

deactivating the first cylinder subset by ceasing injection of liquid fuel to the first cylinder subset while continuing to operate remaining cylinders of the plurality of cylinders with liquid fuel; and is

During the gradual start, the amount of the gaseous fuel is increased relative to the liquid fuel for the remaining cylinders.

2. The engine control method according to claim 1, wherein the amount of the gaseous fuel is increased to the initial amount with respect to the liquid fuel during the gradual start.

3. The engine control method of claim 1, wherein determining a cylinder deactivation event comprises:

monitoring an engine load and an engine speed of the dual-fuel internal combustion engine; and is

Determining the cylinder deactivation event when the engine load is below a threshold load and the engine speed is below a threshold speed for a predetermined period of time.

4. The engine control method of claim 3, wherein determining a cylinder deactivation event further comprises:

determining whether one or more of a coolant temperature, an intake manifold temperature, an ambient temperature, and an intake air temperature are within a predetermined temperature range; and is

It is determined whether one or more diagnostic faults have not been triggered.

5. The engine control method of claim 1, wherein determining a cylinder deactivation event comprises:

a cylinder deactivation mode input is received from an operator.

6. The engine control method according to claim 2, wherein the step-up period is a first step-up period, and the step-up period is a first step-up period, the engine control method further comprising:

continuing to operate the remaining cylinders in a first deactivation cycle;

identifying a second subset of cylinders from the remaining cylinders to be deactivated;

decreasing the amount of the gaseous fuel relative to the liquid fuel from the initial amount during a second step-down for all remaining cylinders, and then stopping injecting gaseous fuel;

deactivating a second cylinder subset by stopping injection of liquid fuel in the second cylinder subset while operating the second cylinder subset with liquid fuel, the third cylinder subset including cylinders of the remaining cylinders other than the second cylinder subset; and is

During a second step start, increasing the amount of the gaseous fuel relative to the liquid fuel for the third cylinder subset.

7. The engine control method according to claim 1, wherein the step-up period is a first step-up period, the engine control method further comprising:

exiting the cylinder deactivation mode, comprising:

stopping injecting gaseous fuel while continuing to inject liquid fuel into the remaining cylinders;

activating the first cylinder subset, including injecting liquid fuel into the first cylinder subset; and is

Injecting gaseous fuel into all of the plurality of cylinders to increase the amount of the gaseous fuel relative to the liquid fuel during a second step start.

8. An engine control method comprising:

operating a dual-fuel internal combustion engine including first and second cylinder subgroups configured to receive liquid and gaseous fuels, a liquid fuel control module, a first gaseous fuel control module associated with the first cylinder subgroup, and a second gaseous fuel control module associated with the second cylinder subgroup;

determining a cylinder deactivation event;

while instructing the liquid fuel control module to continue operating the first and second cylinder subsets with the liquid fuel during the gradual stop, instructing the first and second gaseous fuel control modules to gradually begin decreasing the amount of the gaseous fuel in the first and second cylinder subsets relative to the liquid fuel from an initial amount and then stop injecting gaseous fuel in the first and second cylinder subsets during the gradual stop;

deactivating the first cylinder subset by instructing the liquid fuel control module to stop injecting the liquid fuel in the first cylinder subset while continuing to inject the liquid fuel in the second cylinder subset; and is

Instructing the second gaseous fuel control module to increase the amount of the gaseous fuel to the initial amount relative to the liquid fuel during a first step start of the second cylinder subset; and

exiting the cylinder deactivation mode, comprising:

instructing the second gaseous fuel control module to progressively decrease the amount of gaseous fuel relative to liquid fuel in the second cylinder subgroup from an initial amount;

activating the first cylinder subset by instructing the liquid fuel control module to inject liquid fuel in the first cylinder subset; and

instructing the first and second gaseous fuel control modules to increase the amount of gaseous fuel relative to liquid fuel in the first and second cylinder subgroups to the initial amount during a second step start.

9. An engine control system comprising:

a dual fuel internal combustion engine including a plurality of cylinders configured to receive a liquid fuel and a gaseous fuel, the plurality of cylinders divided into a first cylinder subset and a second cylinder subset;

a fuel system including a liquid fuel source and a gaseous fuel source;

a controller, a liquid fuel control module, and at least one gaseous fuel control module, each of the controller, liquid fuel control module, and at least one gaseous fuel control module associated with the first and second cylinder subgroups and communicatively connectable over a network;

the controller has an operating mode in which the plurality of cylinders operate and a cylinder deactivation mode;

the controller in the operating mode is configured to instruct the liquid fuel control module and the at least one gaseous fuel control module to operate the plurality of cylinders in a dual fuel mode in which both the liquid fuel and the gaseous fuel are supplied to the plurality of cylinders; and is

The controller in the cylinder deactivation mode is configured to:

while instructing the liquid fuel control module to continue operating the plurality of cylinders with the liquid fuel during a gradual stop, instructing the at least one gaseous fuel control module to gradually start decreasing the amount of the gaseous fuel relative to the amount of the liquid fuel in all of the plurality of cylinders from an initial amount during the gradual stop and then stop injecting the gaseous fuel;

instructing the liquid fuel control module to deactivate the first cylinder subset by stopping injection of the liquid fuel into the first cylinder subset while continuing to inject liquid fuel into the second cylinder subset after the gradual stop period; and is

After deactivating the first cylinder subset, instructing the liquid fuel control module and the at least one gaseous fuel control module to transition to the dual fuel mode in the second cylinder subset during a gradual start.

10. The engine control system of claim 9, wherein in the dual fuel mode, the controller is configured to:

instructing the liquid fuel control module to inject an amount of the liquid fuel into each active cylinder of the dual-fuel internal combustion engine and instructing the at least one gaseous fuel control module to inject an amount of the gaseous fuel into each active cylinder of the dual-fuel internal combustion engine.

11. The engine control system of claim 9, wherein transitioning to the dual fuel mode in the second cylinder subgroup during the gradual start further comprises:

instructing the at least one gaseous fuel control module to increase the amount of the gaseous fuel to the initial amount relative to the liquid fuel during the gradual start of the second cylinder subgroup.

12. The engine control system of claim 9, wherein the at least one gaseous fuel control module further comprises:

a first gaseous fuel control module associated with the first cylinder subgroup and a second gaseous fuel control module associated with the second cylinder subgroup.

13. The engine control system of claim 9, wherein the cylinder deactivation mode is initiated after the controller determines a cylinder deactivation event.

14. The engine control system of claim 12, wherein the controller is configured to determine a cylinder deactivation event if:

the engine load is below a threshold load and the engine speed is below a threshold speed for a predetermined period of time;

one or more of the coolant temperature, the intake manifold temperature, the ambient temperature, and the intake air temperature are within a specific temperature range, and

a diagnostic fault has not yet been triggered.

15. The engine control system of claim 12, wherein the controller is configured to determine a cylinder deactivation event after receiving a cylinder deactivation mode input from an operator.

16. The engine control system according to claim 11, wherein the step-up period is a first step-up period, and the step-up period is a first step-up period, the controller being further configured to:

continuing to operate the second cylinder subset in a first deactivation cycle; and is

Deactivating the second cylinder subset after a first deactivation cycle and reactivating the first cylinder subset by:

while instructing the liquid fuel control module to continue operating the second cylinder subset with the liquid fuel during a second gradual stop, instructing the at least one gaseous fuel control module to reduce the amount of the gaseous fuel in the second cylinder subset relative to the liquid fuel from an initial amount during the second gradual stop and then stop injecting gaseous fuel in the second cylinder subset;

instructing the liquid fuel control module to stop injecting the liquid fuel into the second cylinder subset and to begin injecting liquid fuel into the first cylinder subset; and is

Instructing the at least one gaseous fuel control module to increase the amount of the gaseous fuel relative to the liquid fuel during a second step start of the first cylinder subset.

17. The engine control system of claim 9, wherein the gradual start period is a first gradual start period, the controller being further configured to exit the cylinder deactivation mode by:

instructing the at least one gaseous fuel control module to stop injecting gaseous fuel into the second cylinder subset while instructing the liquid fuel control module to inject liquid fuel into the first and second cylinder subsets;

and is

Instructing the at least one gaseous fuel control module to inject gaseous fuel into the first cylinder subset and the second cylinder subset to increase the amount of the gaseous fuel relative to the liquid fuel during a second step start.